Many known flat panel displays use a planar edge-lit backlight/light emitting assembly in which the light from one or more light sources is injected into the backlight (either using white light or cycling through individual red, green, blue (RGB) colors) and is shared by all pixels in a display during a light emission cycle. While the light is ON, pixels emit light either through selected optical pathways via a twist of liquid crystals (as in an LCD) or through a light valve structure in a Micro-opto-electromechanical systems (MOEMS) panel (opaquing shutters or Frustrated Total Internal Reflection (FTIR) light extraction mechanisms). During the same time the ON pixels are emitting light, the OFF pixels will also be in the glow of the backlight thereby reducing the contrast ratio.
Some known flat panel display systems utilize segmented backlights/light emitting assemblies 150 that are specifically designed to turn off a portion of the backlight behind blocks of rows of pixels. Such display systems require individual electronic controls, light sources 152a-e and waveguides for each block 101a-j (see FIGS. 1A and 1B). Loading data for only the row blocks that have the light source ON insures that the row blocks with the light sources OFF will be dark, increasing the contrast ratio but reducing the total average output of light.
When a backlight is divided into multiple elements, the alignment of the individual backlight blocks becomes a mechanical assembly issue. First the alignment of each block 101a -j needs to be maintained in tight physical alignment with the light injection faces 157 of the respective LED light sources 152a-e, while maintaining tight physical alignment of the top surface 156 with the LCD or MOEMS panel 154 for light injection into the defined active display area of the panel associated with each block. In addition, it is important to maintain individual alignment of the adjoining side wall faces 158 between the neighboring adjacent blocks 101a -j to limit the amount of light cross talk between the individual blocks.
With individual backlight elements, each block would need its own XYZ alignment and fastening constraints, which would change the total internal reflection (TIR) light to FTIR light and cause the backlight/light emitting assembly to glow, decreasing the contrast ratio.